You are currently viewing [3 in 1]Pain Peripheral Mechanisms : [Med Notes+MCQ+Q&A]

PERIPHERAL MECHANISMS OF PAIN [ MIND MAP/MEDICAL NOTES ]

  • Primary Afferent Nociceptor
    • Peripheral nerve structure
      • Axons of 3 types of neurons: primary sensory afferents, motor neurons, sympathetic postganglionic neurons
    • Location of cell bodies: dorsal root ganglia within vertebral foramina
    • Types of primary afferent fibers
      • A-beta (Aβ): respond to light touch and moving stimuli, present in skin nerves
      • A-delta (Aδ): small diameter myelinated fibers, present in skin and deep somatic and visceral structures
      • C fibers: unmyelinated fibers, present in skin and deep somatic and visceral structures, respond to intense stimuli
    • Primary afferent nociceptors: respond to noxious stimuli (heat, intense cold, mechanical distortion, pH changes, chemical irritants)
      • TrpV1 (vanilloid receptor): mediates perception of some noxious stimuli, activated by heat, acidity, endogenous mediators, capsaicin

PERIPHERAL MECHANISMS OF PAIN [CLINICAL SCENARIO MCQ 

Scenario 1:

A patient is experiencing pain in their hand after burning it on a hot stove. The healthcare provider suspects that the pain is being caused by activation of primary afferent nociceptors in the hand.

Question: What type of primary afferent fiber is most likely responsible for the patient’s pain?

Option 1: A-beta fibers

Option 2: A-delta fibers

Option 3: C fibers Option 4: Motor neurons

Answer: Option 2: A-delta fibers

Explanation:

A-delta fibers are small diameter myelinated fibers that are present in nerves to the skin and to deep somatic and visceral structures. They respond maximally to intense (painful) stimuli and produce the subjective experience of pain when activated. In this scenario, the patient’s hand was burned, which is an intense stimulus that would likely activate A-delta fibers and cause pain.

Scenario 2:

A patient is experiencing pain in their lower back after lifting a heavy object. The healthcare provider suspects that the pain is being caused by activation of primary afferent nociceptors in the back muscles.

Question: What type of primary afferent fiber is most likely responsible for the patient’s pain?

Option 1: A-beta fibers

Option 2: A-delta fibers

Option 3: C fibers

Option 4: Motor neurons

Answer: Option 3: C fibers

Explanation: C fibers are unmyelinated fibers that are present in nerves to the skin and deep somatic and visceral structures. They respond maximally to intense (painful) stimuli and produce the subjective experience of pain when activated. In this scenario, the patient’s back muscles were subjected to heavy mechanical stress, which is an intense stimulus that would likely activate C fibers and cause pain.

Scenario 3:

A patient is experiencing pain in their tooth after biting down on something hard. The healthcare provider suspects that the pain is being caused by activation of primary afferent nociceptors in the tooth.

Question: What type of primary afferent fiber is most likely responsible for the patient’s pain?

Option 1: A-beta fibers

Option 2: A-delta fibers

Option 3: C fibers

Option 4: Motor neurons

Answer: Option 2: A-delta fibers

Explanation: A-delta fibers are small diameter myelinated fibers that are present in nerves to the skin and deep somatic and visceral structures. They respond maximally to intense (painful) stimuli and produce the subjective experience of pain when activated. In this scenario, the patient’s tooth was subjected to intense mechanical stress, which is an intense stimulus that would likely activate A-delta fibers and cause pain.

Scenario 4:

A patient is experiencing pain in their foot after stepping on a sharp object. The healthcare provider suspects that the pain is being caused by activation of primary afferent nociceptors in the foot.

Question: What type of primary afferent fiber is most likely responsible for the patient’s pain?

Option 1: A-beta fibers

Option 2: A-delta fibers

Option 3: C fibers

Option 4: Motor neurons

Answer: Option 2: A-delta fibers

Explanation:

A-delta fibers are small diameter myelinated fibers that are present in nerves to the skin and deep somatic and visceral structures. They respond maximally to intense (painful) stimuli and produce the subjective experience of pain when activated. In this scenario, the patient’s foot was subjected to intense mechanical stress, which is an intense stimulus that would likely activate A-delta fibers and cause pain.

Scenario 5:

A patient is experiencing pain in their stomach after eating a spicy meal. The healthcare provider suspects that the pain is being caused by activation of primary afferent nociceptors in the stomach.

Question: What type of primary afferent fiber is most likely responsible for the patient’s pain?

Option 1: A-beta fibers

Option 2: A-delta fibers

Option 3: C fibers

Option 4: Motor neurons

Answer: Option 3: C fibers

Explanation: C fibers are unmyelinated fibers that are present in nerves to the skin and deep somatic and visceral structures. They respond maximally to intense (painful) stimuli and produce the subjective experience of pain when activated. In this scenario, the patient’s stomach was subjected to the intense chemical stimulus of spicy food, which would likely activate C fibers and cause pain.

 

Dr. Arin Nandi

Passionate About Medical Science & Helping Future Doctors Achieve Top Ranks In Medical Exams. He is professionally a dentist as well as a public health expert from JIPMER working in govt.health department
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